Semiconductor workpiece apparatus

ABSTRACT

Various embodiments of an apparatus for holding and processing semiconductor workpieces are provided. In one aspect, an apparatus is provided that includes a first base, a second base and three elongated members coupled to and between the first base and the second base. The three elongated members are spatially arranged so that a semiconductor workpiece may be positioned therebetween. Each of the elongated members has a first lateral edge, a second lateral edge and at least one radially inwardly projecting member. The at least one radially inwardly projecting member has a third lateral edge, a fourth lateral edge and an upper surface for receiving a portion of the semiconductor workpiece and a lower surface. The third lateral edge is displaced laterally inward from the first lateral edge and the fourth lateral edge is displaced laterally inward from the second lateral edge.

This application is a divisional of prior U.S. patent application Ser.No. 10/261,368 filed on Sep. 30, 2002 now U.S. Pat. No. 6,939,132.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to semiconductor processing, and moreparticularly to semiconductor workpiece holder and processing chambersusing the same.

2. Description of the Related Art

Tube furnaces are widely used in semiconductor processing for a varietyof different types of process steps. Examples of tube furnace processesare legion and include devices suited for chemical vapor deposition(“CVD”), annealing, and oxidation to name just a few. In manyconventional tube reactors, scores of semiconductor wafers arepositioned in a rack or boat composed of quartz. Conventional boatdesigns usually consist of three or more rails connected at each end toa cap. The rails are spaced apart and provided with a plurality oflaterally spaced rings or inwardly projecting tabs that are designed tosupport the wafers. After loading, the boat is positioned in the reactorand, depending upon the particular process involved, reactive gases areintroduced therein and exhausted therefrom.

Conventional boat designs exhibit several disadvantages. In thoseconventional boat designs that include a plurality of vertically spacedrings for supporting individual wafers, the rings themselves are subjectto frequent fracture and warping as a result of thermal stresses. Afractured ring requires the boat to be taken out of service andsubjected to a time intensive and costly repair procedures. Ring warpingcan skew the characteristics of films deposited on the wafer. Thisskewing in film properties stems largely from the fact that many typesof CVD processes are mass transfer limited. In such processes, the pitchor spacing between the wafers in the boat is critical in order to reducethe impact of mass transfer limitations. If one or more rings supportingthe wafers become warped, the critical spacing may be changed and resultin poor film quality during deposition.

In those conventional designs that incorporate inwardly projecting tabsin lieu of rings, there remains the problem of localized cooling of thewafers as a result of conductive heat transfer between the wafer and thetabs. Conventional tab designs present a relatively large footprint incontact with the wafer, resulting in conductive heat transfer that issufficient to produce a localized cooling of the wafer. This localizedcooling produces a perturbation in the boundary layer formation in thevicinity of the tab. The disruption in the boundary layer formation canagain lead to unanticipated film characteristics, particularly in masstransfer limited reactions, such as high temperature and mediumtemperature oxidation processes.

The present invention is directed to overcoming or reducing the effectsof one or more of the foregoing disadvantages.

SUMMARY OF THE INVENTION

In accordance with one aspect of the present invention, an apparatus isprovided that includes a first base, a second base and three elongatedmembers coupled to and between the first base and the second base. Thethree elongated members are spatially arranged so that a semiconductorworkpiece may be positioned therebetween. Each of the elongated membershas a first lateral edge, a second lateral edge and at least oneradially inwardly projecting member. The at least one radially inwardlyprojecting member has a third lateral edge, a fourth lateral edge and anupper surface for receiving a portion of the semiconductor workpiece anda lower surface. The third lateral edge is displaced laterally inwardfrom the first lateral edge and the fourth lateral edge is displacedlaterally inward from the second lateral edge.

In accordance with another aspect of the present invention, an apparatusis provided that includes a processing chamber for processing at leastone semiconductor workpiece. A rack is positioned in the processingreactor for holding the at least one semiconductor workpiece. The rackhas a first base, a second base, and three elongated members coupled toand between the first base and the second base. The three elongatedmembers are spatially arranged so that at least one semiconductorworkpiece may be positioned therebetween. Each of the elongated membershas a first lateral edge, a second lateral edge and at least oneradially inwardly projecting member. The at least one radially inwardlyprojecting member has a third lateral edge, a fourth lateral edge and anupper surface for receiving a portion of the at least one semiconductorworkpiece and a lower surface. The third lateral edge is displacedlaterally inward from the first lateral edge and the fourth lateral edgeis displaced laterally inward from the second lateral edge.

In accordance with another aspect of the present invention, an apparatusis provided that includes a first quartz base, a second quartz base andthree elongated quartz members coupled to and between the first quartzbase and the second quartz base. The three elongated quartz members arespatially arranged so that a plurality of semiconductor workpieces maybe positioned therebetween in spaced-apart relation. Each of theelongated quartz members has a first lateral edge, a second lateral edgeand a plurality of radially inwardly projecting members. Each of theplurality of radially inwardly projecting members has a third lateraledge, a fourth lateral edge and an upper surface for receiving a portionof one of the plurality of semiconductor workpieces and a lower surface.The third lateral edge is displaced laterally inward from the firstlateral edge and the fourth lateral edge is displaced laterally inwardfrom the second lateral edge.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other advantages of the invention will become apparentupon reading the following detailed description and upon reference tothe drawings in which:

FIG. 1 is a pictorial view of an exemplary embodiment of an apparatussuitable for holding one or more semiconductor workpieces in accordancewith the present invention;

FIG. 2 is a magnified side view of a selected portion of FIG. 1 inaccordance with the present invention;

FIG. 3 is a cross-sectional view of FIG. 1 taken at section 3-3 inaccordance with the present invention;

FIG. 4 is a magnified view of a selected portion of FIG. 3 that includesa radially inwardly projecting support member in accordance with thepresent invention;

FIG. 5 is cross-sectional view like FIG. 4, but depicts an exemplaryconventional support member;

FIG. 6 is a side view like FIG. 2, but depicts an alternate exemplaryembodiment of the apparatus in accordance with the present invention;and

FIG. 7 is a cross-sectional view like FIG. 4, but depicts anotheralternate exemplary embodiment of the apparatus in accordance with thepresent invention.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

In the drawings described below, reference numerals are generallyrepeated where identical elements appear in more than one figure.Turning now to the drawings, and in particular to FIG. 1, therein isshown a pictorial view of an exemplary embodiment of an apparatus 10suitable for holding one or more semiconductor workpieces 12, 14. Theapparatus 10 is commonly referred to in the industry as a rack or boat.Only two workpieces 12 and 14 are shown for simplicity of illustration.However, the number of semiconductor workpieces 12, 14 that may be heldby the boat 10 is variable. It is envisioned that the boat 10 may beconfigured to hold one or up to many scores of workpieces as desired.The semiconductor workpieces 12, 14 may be semiconductor wafers,semiconductor-on-insulator wafers, or virtually any other type ofworkpiece used in circuit manufacture.

The boat 10 is designed to be inserted into a processing chamber 15. Theprocessing chamber 15 may be any of a variety of chambers used insemiconductor processing, such as, for example, CVD chambers, lowpressure CVD chambers, plasma enhanced CVD chambers, annealing chambers,oxidation chambers or the like.

The boat 10 consists of a disk-like base 16, a disk-like base 18, andthree or more elongated members or rods 20, 22 and 24 coupled betweenthe bases 16 and 18. The rods, 20, 22 and 24 are spatially arranged sothat the semiconductor workpieces 12, 14 may be positioned therebetween.In order to support the semiconductor workpieces 12, 14, each of therods 20, 22 and 24 is provided with one or more radially inwardlyprojecting members 26. The set of members 26 for the rod 22 is notvisible in FIG. 1. The structure and function of the members 26 will bedescribed in more detail below in conjunction with FIGS. 2, 3 and 4. Thepictorial view in FIG. 1 actually depicts the boat 10 upside down toreveal the underside structure of the base 18. When inserted into theprocessing chamber 15, the base 18 of the boat 10 is positioned on apedestal 27. To facilitate seating of the base 18 on the pedestal 27 thebase 18 may be provided with a projecting flange 28 and one or morealignment shims 30 and 32.

The various structures of the boat 10 may be fabricated from, forexample, quartz, silicon, silicon carbide or the like. The materialsselected for the various structures of the boat 10 are generallyselected for their relative chemical inertness. The various structuralmembers of the boat 10 may be joined by welding, adhesives or the like.For example, where the bases 16 and 18 and the members 20, 22 and 24 arecomposed of quartz, the members 20, 22 and 24 may be joined to the bases16 and 18 by well-known glass welding techniques Optionally, the entireboat 10 may be integrally formed.

To better illustrate the structure and function of the inwardlyprojecting members 26, a side view of a selected portion 34 of FIG. 1that includes portions of the member 20 and the semiconductor workpieces12 and 14 is illustrated at a higher magnification in FIG. 2. Thedescription of the structure and function of any one of the members,e.g., 20, 22 or 24, is illustrative of the other members. It is helpfulat this point to refer also to FIG. 3, which is a cross-sectional viewof FIG. 1 taken at section 3-3. Note that the section for FIG. 3 istaken through the portions of the members 20, 22 and 24 such that theirrespective inwardly projecting members 26 that physically support thesemiconductor workpiece 14 are also shown in section. As shown in FIG.2, each of the inwardly projecting members 26 includes an upper surface36 for receiving a portion of one of the semiconductor workpieces 12,14. The members 26 may be integrally formed with the member 20 or formedseparately and coupled thereto by welding, adhesives or other well-knownfastening techniques.

The spacing or pitch X between adjacent of the members 26 may betailored as necessary to accommodate the particular reaction kineticsfor the processes in which the boat 10 will be used. The skilled artisanwill appreciate that in reactions that are mass transfer limited, suchas, for example, medium and high temperature oxide CVD through thereaction of silane and nitrous oxide, the pitch X may be selected tosatisfy the Theile modulus requirements for the reaction in question.The pitch between adjacent members 26 may be the same. Optionally, someof the members 26 may be spaced with a pitch X and others with anotherpitch X′. Providing different pitches may be desirable where, forexample, it is necessary to compensate for a smaller than expected flatzone in the processing chamber 15 (See FIG. 1).

The configuration of the inwardly projecting members 26 is selected toprovide a highly thermally resistive, that is, less thermally conductiveheat transfer pathway from the semiconductor workpieces 12, 14 to theboat 10. This is accomplished by providing the members 26 with afootprint that is substantially reduced over that provided byconventional boat designs. As shown more clearly in FIG. 4, which is amagnified view of a portion of FIG. 3 that encompasses the rod 22 and aportion of the semiconductor workpiece 14, the rod 22 includes lateraledges 38 and 40. The reduced profile of the inwardly projecting member26 is provided by forming it with lateral edges 42 and 44 that areinwardly displaced respectively from the lateral edges 38 and 40 of therod 22. This smaller footprint for the inwardly projecting member 26provides more thermal resistance against conductive heat transferbetween the semiconductor workpiece 14 and the member 26. Thisdiminished thermal conduction will reduce the localized cooling of thesemiconductor workpiece 14 in the vicinity of the rods 20, 22 and 24,which will thereby reduce the impact on boundary layer formation duringthe processing of the workpieces 12 and 14. This reduction in the impacton boundary layer formation is of great importance in mass transferlimited reactions.

The configuration of the rods and in particular the members 26 may becontrasted with a conventional rod design depicted in FIG. 5. FIG. 5 isa cross-sectional view of similar perspective as FIG. 4. Theconventional rod 46 depicted in FIG. 5 includes a region 48 that isresponsible for physically supporting a semiconductor workpiece 50. Therelatively large surface contact area between the portion 48 of the rod46 and the workpiece 50 can lead to significant boundary layer formationas a result of conductive heat transfer during chemical reaction. Thiscan lead to localized distortions in the properties of the films formedon the workpiece 50 near the rod 46.

Alternate exemplary embodiments are envisioned in which the structure ofthe inwardly projecting members is altered to provide even greaterresistance to conductive heat transfer. A first alternate exemplaryembodiment is illustrated in FIG. 6, which is a side view from the samegeneral perspective as FIG. 2, albeit without showing one of thesemiconductor workpieces 12,14. In this illustrative embodiment, themember 122 may be provided with one or more radially inwardly projectingmembers 126 as generally described above. The upper surface 136 of eachmember 126 may be substantially flat in order to accommodate asemiconductor workpiece. However, in this illustrative embodiment, themembers 126 may be provided with a tapered under surface 152. In thisway, the overall bulk of each of the members 126 is reduced over thatprovided by a more symmetric, rectangular configuration.

Another alternate exemplary embodiment incorporating structural featuresto add greater resistance to thermal conduction is shown in FIG. 7,which is a cross-sectional view taken from the same general perspectiveas FIG. 4, albeit without depicting one of the semiconductor workpieces12,14. In this illustrative embodiment, the member 222 is provided withan inwardly projecting member 226 as generally described above. However,one or more holes 254 may be provided in the member 226 in order toreduce the bulk and thus the heat transfer capability of the member 226.The number and configuration of the holes 254 is largely a matter ofdesign discretion. If desired, both tapered profiling and holes may beincorporated into the members 226.

While the invention may be susceptible to various modifications andalternative forms, specific embodiments have been shown by way ofexample in the drawings and have been described in detail herein.However, it should be understood that the invention is not intended tobe limited to the particular forms disclosed. Rather, the invention isto cover all modifications, equivalents and alternatives falling withinthe spirit and scope of the invention as defined by the followingappended claims.

1. An apparatus, comprising: three elongated members spatially arrangedso that at least one semiconductor workpiece may be positioned therebetween; one or more reduced profile support members projecting radiallyinwardly from each of the elongated members, each of the reduced profilesupport members comprising: an upper surface for receiving a portion ofthe at least one semiconductor workpiece; an under surface; a firstlateral edge; and a second lateral edge, wherein each of the elongatedmembers comprises a width substantially greater than a width of the oneor more reduced profile support members projecting radially inwardlytherefrom.
 2. The apparatus of claim 1, further comprising a processingchamber, wherein said three elongated members comprise a rack within theprocessing chamber, and wherein the processing chamber comprises achemical vapor deposition chamber.
 3. The apparatus of claim 1, furthercomprising a processing chamber, wherein said three elongated memberscomprise a rack within the processing chamber, and wherein theprocessing chamber comprises a furnace.
 4. The apparatus of claim 1,wherein the three elongated members comprise quartz.
 5. The apparatus ofclaim 4, wherein three elongated members are coupled between a firstbase and a second base, and wherein the first base and the second basecomprise quartz.
 6. The apparatus of claim 1, wherein the one or morereduced profile support members includes a hole.
 7. The apparatus ofclaim 1, wherein the under surface comprises a tapered surface.
 8. Theapparatus of claim 1, wherein each of elongated members comprises aplurality of spaced-apart reduced profile support members.
 9. Theapparatus of claim 8, wherein each of the reduced profile supportmembers includes a first pitch.
 10. The apparatus of claim 8, wherein afirst portion of the reduced profile support members includes a firstpitch and a second portion of the reduced profile support membersincludes a second pitch.
 11. An apparatus, comprising: a processingchamber for processing at least one semiconductor workpiece; a rackpositioned in the processing chamber, the rack comprising threeelongated members spatially arranged so that the at least onesemiconductor workpiece may be positioned there between, wherein therack has a first base coupled to a first end of the three elongatedmembers and a second base coupled to a second end of the three elongatedmembers; and one or more reduced profile support members projectingradially inwardly from each of the elongated members, each of thereduced profile support members comprising: an upper surface forreceiving a portion of the at least one semiconductor workpiece; anunder surface; a first lateral edge; and a second lateral edge, whereineach of the elongated members comprises a width substantially greaterthan a width of the one or more reduced profile support membersprojecting radially inwardly therefrom.
 12. The apparatus of claim 11wherein the processing chamber comprises a chemical vapor depositionchamber.
 13. The apparatus of claim 11 wherein the processing chambercomprises a furnace.
 14. The apparatus of claim 11 wherein the threeelongated members comprise quartz.
 15. The apparatus of claim 14,wherein the first base and the second base comprise quartz.
 16. Theapparatus of claim 11, wherein the one or more reduced profile supportmembers includes a hole.
 17. The apparatus of claim 11 wherein the undersurface comprises a tapered surface.
 18. The apparatus of claim 11wherein each of elongated members comprises a plurality of reducedprofile support members.
 19. The apparatus of claim 18, wherein each ofthe reduced profile support members includes a first pitch.
 20. Theapparatus of claim 18, wherein a first portion of the one or morereduced profile support members includes a first pitch and a secondportion of the one or more reduced profile support members includes asecond pitch.